A New Concept to Form Arc Cylinders to Parabolic Troughs Using Optimal Forces

Large parabolic concentrating mirrors are an important component of many solar energy systems. They need to be relatively precise against disturbances as gravity, thermal gradients, wind loading, etc. Here, a new method is proposed to transform a cylindrical reflector surface that is easy to manufacture into a parabolic surface for use in large solar concentrators. This is achieved by applying a finite number of optimal point loads using actuators along the back of the cylindrical reflector surface. The paper details a finite element optimization method used to obtain the optimal force magnitudes to transform an arc cylinder into a parabolic trough. It also presents an analysis of the power boost realized at the receiver in going from a circular to parabolic cross-section. The proposed method is analyzed using theoretical derivations, numerical calculations and finite element model calculated in the finite element software ADINA. FEA shape results are optically ray-traced and focal errors are to evaluate the deformed shape. The mechanics can also be used to control other deformable optical surfaces. This concept has potentials to provide precision large parabolic trough concentrators at a substantially lower cost than conventional methods.